U.S. Pat. No. 7,541,914 (Breiner) and U.S. Pat. No. 6,225,897 (Doyle) disclose systems whose objective is to warn motorists that the driver of another vehicle is using a cell phone and is likely, therefore, to be distracted. The entire disclosure of each of those patents is incorporated herein by reference for all purposes. There remains a need for additional means for the controlling the use of wireless control devices (WCDs) in motor vehicles, including for example means for preventing drivers of motor vehicles from sending text messages, and means for limiting the duration of voice calls.